Deflection circuit



, w. SCHRODER DEFLEC'IION CIRCUIT 3 Sheets-Sheet 2 Filed Oct. 13, 1953 INV EN TORI W schrb der June 25, 1957 w. cHRODER v 2,797,359 w DEFLEQTION CIRCUIT Filed on. 15,195; a Shets-$heet a I mmvrom W' schr der DEFLECTION ClRCUlT Willi Schriider, Ulm (Danube), Germany, assignor to Telefunken Gesellscliaft fuer drahtlose Telegraphic G. m. b. H., Hannover, Germany Application October 13, 195$,Serial No. 385,851

Claims. priority, application Germany @ctober 15, 1952 9 Claims. (Cl. 315-27) The present invention relates to deflection circuits of the type employed for providing a time base in connection with cathode ray tubes for deflection of an electron beam.

Magnetic deflection systems are often employed in present day systems for deflecting an electron beam in a cathode ray tube. These magnetic deflection systems employ in general two coils arranged about the neck of the cathode :ray tube and in which coils saw tooth wave forms of ditferent frequencies are generated.

In one arrangement for generating saw tooth current Wave forms for line deflection of TV picture tubes and with which arrangement the present invention may be advantageously used, a condenser is provided. which by means of a diode which is rendered conductive during ihBfO-IW'Hlfd. stroke of the. saw tooth Wave form,.supplies a constant voltage to the winding of an auto transformer. By means of this constant voltage, alinearly increasing current is generated in the transformer and as a result also in the deflection coil coupled thereto.

The loss of energy in the deflection circuit is compensated during the forward stroke of the. saw tooth wave form by the final sweep amplifier, which supplies such a current that the diode conducts during the entire forward stroke of the saw tooth wave form. The diode is rendered non-conductive when current flow through the final sweep amplifier is cut-off by a saw tooth synchronizing; impulse fed to the control grid of the final sweep amplifier tube; In particular, the final sweep amplifier is cut-olf by the negative flyback of a saw tooth synchronizing impulse fed to its control grid. When the amplifier tube is cut off its anode voltage will rise, thus raising the voltage of the cathode of the diode beyond its anode voltage. The diode will therefore cease to conduct and the transformer as well as the deflecting coil and the stray capacities in the circuit go through a free half cycle variation at the end of which, the voltage across the transformer is: reversed and as a result the control diode again becomes conductive so that the above cycle may again be repeated. In addition, during the fly back period of the saw tooth synchronizing impulse, a high positive peaked voltage is developed across. the transformer which is rectified by another diode. The rectified high peaked voltage is connected to the accelerating anode of a cathode ray tube and serves to accelerate the electron beam in the cathode ray tube.

A more detailed description of the above arrangement may be found in an article by R. Andrieu, titled, The line deflection circuit with auto transformer which appeared in a Telefunken paper, volume 95 in the year 1952.

Accunate control of the sweep amplitude is an absolute requirement for line deflection circuits involving simultaneous generation of high voltages for picture tubes. It is necessary in order to accurately control the line deflection amplitude to compensate for variations in electrical value of deflection transformers, tubes, as well as for voltage source variationsand the like.

2,797,359 Fatented June 25, 1957 The amount 'of deflection of. the electron beam in a. cathode ray tube depends not only on the amplitude of the saw tooth current Wave form that flows through the deflection coil but also on the amplitude of the accelerating voltage to which the electron beam is exposed. Since the saw tooth current Wave form and the accelerating voltage are produced in the same circuit, it is obvious that an adjustment, of, for instance, the amplitude of the saw tooth current wave form will produce a concomittant change in amplitude {of the accelerating voltage. The sweep amplitude is, on the one hand, directly proportional to the deflection current flowing through the deflection coil, and on the other hand, inversely proportional to the square root of the accelerating voltage.

It is often desired to regulate the sweep amplitude without affecting the focus of the electron beam on the screen of the image tube. This may be performed by adjusting; the sweep current amplitude while at the same time maintaining the high voltage, which is obtained during .the fly back period, constant. On the other hand it may also be desired to adjust the focus of the electron beam on the screen of the picture tube. This focus adjustment may be performed by changing the magnetic field strength of a focussing magnet used with magnetically focussed cathoderay tubes. If one, however, desires to employ a permanent magnet without additionalfocusing coils or without the necessity of adjusting the magnetic field strength, the beam may be focussed by changing the value of the accelerating voltage. However, as already pointed out, a change in accelerating voltage will produce a change in. the sweep amplitude, which is inversely proportional to the square root of the accelerating voltage.

Two ways are known for making the desired adjustment of the sweep amplitude. The first Way concerns the adjustment of the fly back time, on which the magnitude of the generated high voltage as well as the deflection. amplitude is dependent. The second way concerns the changing of the regulated anode voltage of the final sweep amplifier tube in which case, the saw tooth amplitude will be directly proportional to the accelerating voltage. In order to maintain a predetermined amplitude of, the sweep, the saw tooth current must change as the square root of the accelerating voltage. With this relationship of sweep current and accelerating voltage, a change in the size of the raster will result with changes in sweep amplitude.

The adjustment of the anode voltage may be made, 13.8 known in the art, by means of a variable resistor con: nected in series with the anode supply voltage. The disadvantage of adjusting the anode voltage with the above mentioned variable resistor lies in the fact that a certain amount of power will be dissipated by the resistor, thus requiring a higher initial anode supply voltage. One of the objects of the present invention is to provide a control arrangement for adjusting the anode voltage of the final sweep amplifier tube in such manner that additional power requirements are unnecessary. This is accomplished by making a variable connection of the anode of the final sweep amplifier tube with a transformer. A uniform adjustment is made possible by coupling the final sweep amplifier tube parallel to a portion of the transformer & remains constant over the adjusting range, a change in fly back time will occur with anode voltage adjustments inasmuch as the tube capacity is transformed at the deflection coil into a greater or smaller value with the ad- :justm'ent of the adjustable inductances. The adjusting arrangement may on the other hand he :so designed that the total inductance of the series connected variable inductances instead of being held constant, as described above, may be so dimensioned that the total inductance value varies in the same sense, or direction, as the inductance which has its free end terminal :connected to the higher alternating voltage point on the transformer. constant with an adjustment of the anode voltage so that a sharp anode voltage adjustment can be made. i In order to obtain other arbitrary adjusting characteristics, it is possible to connect, for instance, at least In this case the fly back time will remain Y one capacitor in parallel with atleast one of the two series connected inductances. i From the above discussion it will be apparent that it is an object of the present invention to provide a beam deflection circuit for cathode ray tubes in which the sweep amplitude and the high direct current voltage, generated in the beam deflection circuit, may be independently adjusted. It is yet another object of the present lnvention to provide a beam deflection circuit for cathode ray tubes in which the sweep amplitude may be varied linearly with relation to the high direct current voltage.

It is yet another object of the present invention to pro- .vide a beam deflection circuit for cathode ray tubes in which the electron beam focus may be changed by ad- Fig. 6 shows a modification of the circuit arrangement of Fig. 1;

Fig. 7 shows yet another modification of the circuit arrangement of Fig. 1; and

Fig. 8 shows yet other curves having characteristics different from those illustrated in Figs. 3 and 4.

Fig. 1 shows one example of a circuit in accordance with the invention and serves for explaining the operation of the circuit in accordance with the invention. It is assumed that the condenser is charged and as shown in Fig. l. The diode 2, during the forward stroke of the synchronizing impulse supplied by the sweep generator 5', connects a substantially constant voltage to the transformer winding 3 which is illustrated as, being an auto transformer. As a result of the constant voltage connected to the transformer a linearly increasing current is generated in the transformer winding 3 as well as in the deflecting coil 4 which is coupled to the winding 3. The loss of energy in the circuit is compensated during the forward stroke of the synchronizing by the final sweep amplifier 5. The amplifier 5 supplies such a current to the transformer that the diode tube 2 conducts during the entire forward stroke of the synchronizing impulse.

' ,When the tube 5 is cut off by the negative fly back porjusting the accelerating voltage without changing, when I so desired, the sweep amplitude.

Yet another object of the present invention is to provide a beam deflecting circuit for cathode ray tubes in which the fly-back time may be accurately controlled. I

With the above objects in view the present invention mainly consists of a deflection circuit for generating in an inductance a current having a saw tooth wave form and for simultaneously generating a high direct current voltage, comprising, a condenser adapted to have a direct current voltage across its terminals, switching means connected in series with the condenser for applying the voltage across the terminals of the condenser to the inductance when the switching means is actuated, a transformer having awinding a first portion of which is coupled with the inductance, an amplifier having an anode, the amplifier controlling the operation of the switching means, and a first and a second inductance connected in series to form a junction to which the anode of the amplifier tube is connected, the end terminals of the first and second inductances being connected across a second portion of the transformer winding, at least one of the inductances being variable over a predetermined adjusting range.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying' drawings, in which:

Fig. 1 shows a circuit diagram of a deflection circuit in accordance with the present invention; Fig. 2 shows the various curves obtained by plotting he voltage at the deflection coil versus the accelerating voltage at terminal H in the circuit arrangement of Fig. 1;

Fig. 3 shows the curves obtained by plotting the variations in inductance versus core displacement of a control arrangement in accordance with the invention;

Fig. 4 shows another set of curves having different characteristics from those illustrated in Fig. 3;

i Fig. 5 shows schematically, a control arrangement'used in a deflection circuit, in accordance with the invention;

tion of the synchronizing impuse which has an approximately saw tooth wave form, the diode 2 will likewise be cut off. As a result the transformer 3 as Well as the deflecting coil 4 and stray capacities in the circuit go through a free half cycle variation, at the end of which the voltage across the transformer is reversed, and as a result the control diode 2 is again permitted to conduct. The entire cycle is again repeated when the forward stroke of the next syunchronizing impulse reaches the control grid 1' of the final sweep amplifier tube 5. In addition, during the fly back period of the saw tooth synchronizing impulse, a high positive peaked voltage is developed across 'the transformer winding 6 which is rectified by diode 7.

I The inductances 8 and 9 are connected in series, the free terminals ofthe inductances 8 and 9, henceforth also referred to as first and second inductances, respectively, being connected across another portion 12 of the transformer 3. The first and second inductances are of the type which may be adjusted in opposite direction so that the total inductance Ls plus L9 remains constant over the entire adjusting range. This adjustment can be effected, for instance, by winding both coils on a common cylindrical coil form having an axial bore. Within the bore may be arranged a movable ferro-magnetic core. By varying the position of the core in the coil form the inductance of one coil will increase While the inductance of the other will decrease. Fig. 2 shows curves exemplifying the different voltage relationships between accelerating voltage and deflection coil voltage that may be obtained for definite relationships between the first and second inductances. Usp represents the voltage at the deflection coil' 4" obtained during the forward stroke of a saw tooth wave form, and is plotted along the abscissa. UH represents the high volt age generated at terminal H and is plotted along the ordinate axis. The high voltage when appropriately con: nected to a cathode ray tube' serves to accelerate the electron beam in the cathode ray tube. If the dimensions of the adjustable inductances are chosen so that the total inductance L8 plus L9 is not maintained constant, but is instead varied in such manner that the total inductance varies in the same sense as does the inductance L9 so that the transformed tube capacity at the deflection coil 4 is compensated, then the fly back time will remain constant during'the adjustment. Curve 21 shown in Fig. 2 shows the adjusting characteristic curve obtained with the last mentioned relationship of the inductances La and L9. The high voltage UH is seen to increase linearly with re-j spect to the deflection amplitude. Curve 22 shows.the deflection amplitude Usp as varying with the square root of the high voltage UH. As may be noted from curve 22.,

a change. in accelerating voltages. Urrproducessubstantially no change of the deflection-amplitudes If the. total inductance change ismore pronounced than that usedfor obtaining curve 21, then the fly back time. will change when an adjustment ofthe sweep amplitude is made. Curve 21 can be transformed into curve 23'if so desired, in which case, an adjustment of the inductances will produce no changein the high voltageUn. The. mannerin which this is accomplished will' be explained hereinafter.

Fig. 3 illustrates in curve form the variations of the individual coil inductances Ls, L9 as well as. the variation of total inductance, Ls, plus L9, with relation to core displacement X, as obtained with the circuit arrangement of Fig. 1. It isapparent from Fig. 3 that the change in inductance'value of the first and second inductances are in opposite direction so that the total inductance. as a function of. core displacement, remains constant. r

If desired, however, the inductances may also be so related so thatthe total inductance, Ls plus L9, changes in the same sense as inductance L9, as shown in Fig. 4. In this case the change in total inductance. can. be so selected that the change in transformed tube capacity at the deflection coil 4 will be compensated, thereby maintaining the fly back time constant when the adjustment is made.

The adjusment mentioned at last always gave an adjustment along a definite curve shownin Fig. 2, namely curve 21, along which curve for each deflection coil voltage Usp there exists a corresponding definite high.voltag e UH.

In accordance with another aspect of th e'invention both mentioned magnitudes Un'and Usp are adjusted independ ently of one another. In this case the first and second inductances are arranged to be independently adjustable. Such independent adjustments of the high voltageUn and of the deflection coil voltage US may be effected with the circuit arrangement illustrated in Fig. 1. To make such independent adjustments of the high voltage and the deflection coil voltage possible, the oppositely directed adjustments of the inductances La and L9 may be effected through the displacement of a high frequency core in the common coil axis, in which case, one of the two coils is constructed as compared withthe other, so that said one coil may be spatially displaced along the coil form with relation to the other. Fig. 5 shows an arrangement wherein one of the two coils may be displaced with relation to the other in accordance with the invention. Both coil sections La and L9 of the inductive voltage divider are arranged on a common coil form 31 and in such manner that the coil, or inductance L9, is rigidly secured to the coil form 31 while the coil, or inductance, L8 is arranged to be displaced in direction of the axis. Inside the tubular coil form 31 is arranged a displaceable high frequency core 32 which serves to change the coil inductances La and L9 in opposite sense, that is, as one in.- creases, the other decreases. It is possible to obtain with this arrangement, adjustments which will follow curves 21, 22 or- 23 of Fig. 2. It is also possible to obtain a high voltage amplitude and adeflection amplitude of any value with this control arrangement. As a result the need for adjusting of focusing magnets to obtain. a sharp beam focus is overcome since a sharp focus settingmay be obtained with the control arrangement in accordance with the invention by changingthe high voltage level.

Fig. 6 shows another embodiment of the invention in which is connected in parallel with the inductance Ls an independently, adjustable inductance 13. The circuit arrangement illustrated in Fig. 6 is similar to that of Fig. 1 in all other respects. The inductance 13 makes it possible to adjust the horizontal: sweep amplitude-while the high: voltage-is maintained at a constant level.

In all of the arrangements described up to now the inductances: La. and. L9 were-adjusted in opposite direction, that.is as theinductance of one increased the inductance of the other decreased, by meansof a commonhigh .frequency core. An. independent adjustment of highv voltage and deflection amplitude could also be obtained, however, by an arrangement wherein the two inductances areseparated and form twomutually independent coilseach of whichis variable. In. this. case the oppositelydirected adjustment of'the first and second inductances is somewhat more difficult to perform since in, this case, theadjustment of the two-inductances must be simultaneously made. This is howeverno limitation since the. adjustment is.not made very often duringactual operation.

Fig. 7' shows. yet another embodiment of the present invention in which two condensers 10 and 11 are respectively connected' in parallel with the coils La. and L9. By assigning suitable values. to the capacitors, these capacitors can be used to yield any desired. variableadjusting, curve so that in this case also the fly back time can be controlled simultaneously with adjustments of the control. arrangement in accordance with the invention in a desired manner.

For certain applications it may be desired to obtain an adjustment of the deflection amplitude wherethe high voltage is heldlconstant. In order to. obtain such an adjustment, the fly back must be changed while the adjustment takes place. The arrangement. heretofore. described in which condensers 10 and 11 were respectively connected in parallel with the inductances La and L9 may be used. for suchpurpose.

As "already noted it is also possible to adjust the horizontal sweep amplitude while holding the high voltage constant by means of an arrangement in whichonly inductances are used as circuit elements.

By increasing the coil spacing in an arrangement where the inductance values of the first and second inductances are changed in opposite directions as a function of core displacement as in Fig. 3, acurve of the inductance variations may be obtained such that the total inductance is considerably changed when making an adjustment, which produces a considerable change in fly back time, while one of the inductances changes in value only slightly during the adjustment, as shown in Fig. 8.

Experiment has shown that it is possible with an arrangement which exhibits the curves shown in Fig. 8 to hold, without any difliculty, the high voltage constant over an adjusting range of 2:15

Another control arrangement in accordance with the invention, exhibiting an adjusting characteristic curve corresponding to that of Fig. 8 may be used, and which involves the connection of a fixed inductance of suitable magnitude in parallel with the coil Ls. In. Fig. 6 the parallel inductance is designated by reference numeral 13, and shown therein as being adjustable, which together with coil 8 forms the inductance La. In this case also, the high voltage, when adjusting the. inductances La, L9, remains constant without having to make any adjustment of the inductance 13. As may be noted from Fig. 8 the inductance La with displacements of the core is' not materially changed.

If the control arrangement in accordance with the invention employs an adjustable inductance L9 which is connected in series with a fixed inductance Ls, then when an adjustment is made, a change in deflection amplitude may also be effected while simultaneously maintaining the high voltage substantially constant.

The invention is not limited to the described embodiments but may be usedwith deflection circuits which do not involve the use of auto transformers but operate instead with any other type of standard transformer.

It will be understood that each of the elements described above, or two or more together, may also find .a useful application in other types of deflection circuits differing from the types described above,

=" While the invention has beenillustrated and described "as embodied in magnetic deflection circuits, it is not intended toibe'limited to the details shown, sincevarious modification sfand structural changes may be made with *outdeparting in any Way from the spirit of the present ;invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for varifous applications without'omitting features that, from the standpoint of prior art, fairly constitute essential charac- "teristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range "of equivalence of the following claims.

A What is claimed as new'and desired to be secured by Letters Patent is:

" IL A deflection circuit for generating in an inductance fa current having a sawtooth wave form' and for simul- "taneously generating a high direct current voltage, comprising in combination; a condenser adapted to have a direct current voltage across its terminals; switching imeans connected in series with said condenser for applying said voltage across said terminals of said con- "denser to the inductance when said switching means is actuated; a transformer having a winding a first portion :of which is coupled with the inductance; an amplifier having an anode, said amplifier controlling the operation of said switching means; and a first and a second inductance connected in series to form a junction to which "said anode of said amplifier tube is connected, the end terminalsof said first and second inductances being con- "nected-across a second'portion of said transformer wind-- ing, at least one of said first and second inductances being variable over a predetermined adjusting range.

" 2. A deflection circuit for generating in a first inductance a current having a saw tooth wave form and for simultaneously generating a high direct current voltage, comprising in combination, a condenser adapted to have :a direct current voltage across its terminals; switching means connected in series with said condenser for applying said voltage across said terminals of said con- 'denser to the first inductance when said switching means is actuated; a transformer having a winding a first portion of which is coupled with the first inductance; an amplifier tube having an anode :and controlling the operation of said switching means; and a pair of adjustable inductances connected in series to form a junction to which said anode of said amplifier tube is connected, the end terminals of said pair of inductances being connected across a second portion of said transformer Winding, said pair of inductances being arranged with respect to each other to be simultaneously adjustable in opposite directions so as to yield a total inductance which is constant over the entire adjusting range.

'3; A deflection circuit for generating in an inductance a current having a sawtooth wave form and for simultaneously generating a high direct current voltage, comprisinga combination, a condenser adapted to have a direct current voltage across its terminals; switching means connected in series with said condenser for applying said voltage across said terminals of said condenser to the inductance when said switching means is actuated; a transformer having a'winding a first portion of which is coupled with the inductance; an amplifier having an anode, said amplifier controlling the operation of said switching means; a first and a second inductance connected in series to form a junction to which said anode of said amplifier tube is connected, the end terminals of said first and second inductances being connected across a second portion of said transformer winding, at least one of said first and second inductances being variable over a predetermined adjusting range; and at, least one condenser alt) connected across at least one of said inductances foriselecting a desiredadjusting curve. y e V 4; A deflection circuit for generating in aninductance a current having a saw tooth. waveform" and for simultaneously generating a high 'direct current. voltage, comprising in combination, a condenser'adapted to have a direct current voltage'across its terminals; switching means connected in series with said condenser for applying 'said voltage across said terminals of said condenser to the inductance when said switching means is actuated; a transformer having a winding afirst portion of which is coupled with the inductance; an amplifier having an anode, said amplifier controlling the operation of said switching 'means; a first and a second inductance connected in series to form a'junction to which said anode of said amplifier tube is connected, the end terminals of said firstand second inductances being connected-across a second portion of said transformer winding, at least one of saidtfirst and second inductances being variable over a predetermined adjusting range; and a third adjustable inductance connected in parallel with one of 'said first and second inductances.

5. A deflection circuit for generating in a first inductance a current having a saw tooth wave form and for simultaneously generating a high direct current voltage, comprising in combination, a condenser adapted to have a direct current voltage across its terminals; switching means connected in series with said condenser for applying said voltage across said terminals of said condenser to the first inductance when said switching means is actuated; a transformer having a winding a first portion of which is coupled with the first inductance; an amplifier. tube having an anode and controlling the operation of said switching means; and a pair of adjustable inductances connected in series to form a junction to which said anode of'said amplifier tube is connected, the end terminals of said-pair of inductances being connected across a second portion of said transformer winding, said pair of inductances being arranged'with respect to each other to be simultaneously adjustable in opposite directions so as to yield a total inductance which is constant over the entire adjusting range, said pair of inductances forming control means for changing the amplitude of the sawtooth wave form while the high direct current voltage remains substantially constant. I V

6. A deflection circuit for cathode ray tubes employing electro-magnetic deflecting coils comprising, in combination, an output transformer, the elec'tro-magnetic deflecting coils being coupled to a first portion of said output transformer; a switching diode; a boost condenser, said diode and said condenser being connected in series across a second portion of said output transformer to develop across said boost condenser a voltage representative of recovered energy cyclically stored in the deflection circuit; a deflection output tube having at least an anode and a cathode; a first and a second inductance connected in series to form a junction, the end terminals of said first and second inductances being connected across a third portion of said output transformer, the junction of said first and second inductances being connected to the anode of said deflection output tube, said inductances having windings adapted to be wound about a tubular coil form; anda high frequency core adapted to be slidably mounted inside the tubular coil form to change the inductance values of said two inductancesin opposite directions.

7. A deflection circuit for cathode ray tubes employingelectromagnetic deflecting coils comprising, in combination, an output transformer; a deflection output tube, having at least an anode and a cathode, the electromagnetic deflecting coils being coupled to the'anode-cathode circuit of saidoutput tube through said output transformer; a switching diode; a boost condenser, said diode and said condenser beingconnected in series across a first portion of said output transformer to develop across said boost condenser a voltage representative of recovered energy cyclically stored in the deflection circuit; and means for adjusting the amplitude of the deflection voltage for the cathode ray tubes, said means including a pair of inductances connected in series across a second portion of said output transformer and having a junction point, the anode of said deflection output tube being connected to said junction point, at least one of said series connected inductances being adjustable to provide a variable coupling between said output tube and said output transformer.

8. A deflection circuit for cathode ray tubes employing electro-magnetic deflecting coils comprising, in combination, an output transformer, the electromagnetic deflecting coils being coupled to a first portion of said output transformer; a switching diode; a boost condenser, said diode and said condenser being connected in series across a second portion of said output transformer to develop across said boost condenser a voltage representative of recovered energy cyclically stored in the deflection circuit; a deflection output tube having at least an anode and a cathode; a first and a second inductance connected in series to form a junction, the end terminals of said first and second inductances being connected across a third portion of said output transformer, the junction of said first and second inductances being connected to the anode of said deflection output tube; means for adjusting at least one of said first and said second inductances to vary the inductance thereof through a predetermined range; and a first and second condenser connected respectively across said first and second inductances for selecting a desired inductance adjusting curve.

9. A deflection circuit for cathode ray tubes employing electromagnetic deflecting coils comprising in combination, an output transformer; a deflection output tube, having at least an anode and a cathode, the electromagnetic deflecting coils being coupled to the anode-cathode circuit of said output tube through said output transformer; a switching diode; a boost condenser, said diode and said condenser being connected in series across a first portion of said output transformer to develop across said boost condenser a voltage representative of recovered energy cyclically stored in the deflection circuit; rectifier means connected to a winding of said output transformer to derive a high voltage from voltage pulses cyclically arising in said output transformer; and means for adjusting the amplitude of the deflection voltage for the cathode ray tubes, said means including a pair of inductances connected in series across a third portion of said output transformer and having a junction point, the anode of said deflection output tube being connected to said junction point, said pair of inductances being simultaneously adjustable in opposite directions to give a total inductance which is constant over the entire adjusting range.

References Cited in the file of this patent UNITED STATES PATENTS 2,523,108 Friend Sept. 19, 1950 2,566,510 Barco Sept. 4, 1951 2,627,052 Helpert et a1 Jan. 27, 1953 2,656,486 Giordano Oct. 20, 1953 

